1. Field of the Invention
The present invention relates to an inertial latch mechanism for latching the actuator in a disk drive device when an external shock is given to the disk drive device, to an actuator lock mechanism having the inertial latch mechanism and holding the actuator at a rest position when the disk drive device is inoperative, to a disk drive device having such actuator lock mechanism, and particularly to a highly reliable inertial latch mechanism which can latch the actuator regardless of the direction in which said shock causes the actuator to rotate.
2. Description of the Related Art
In the current disk drive device, particularly in the portable personal computer such as the notebook-sized personal computer, high reliability for a shock when it is inoperative is demanded. If the head slider mounted on the actuator is moved from the rest position to the data region of the disk surface by the shock when the disk drive device is not operating, the head slider sticks to the data region surface or scratches the data region surface, which leads to a fatal failure. There is an actuator lock mechanism for holding the actuator at the rest position when the disk drive is inoperative, thereby to prevent the actuator from being rotated by a shock and moving to the data region surface.
In the recent disk drive device, the load/unload mechanism of the head slider is considered for preventing the head slider from sticking to the surface of the refuge area or increasing the reliability for the above shock. The load/unload mechanism causes the head slider to refuge without contacting with the disk surface by holding the actuator in a ramp provided in the vicinity of the outer periphery of the disk when the disk drive device is not operating.
There is an actuator lock mechanism using an inertial latch mechanism. In the actuator lock mechanism using the inertial latch mechanism, usually the ramp of the above load/unload mechanism, a magnetic lock mechanism or the like is also used as an actuator hold mechanism. The inertial latch mechanism operates when a shock is given to the disk drive device, and it is a mechanism for latching the actuator by using the inertial force generated by the given shock. This inertial latch mechanism can latch the actuator against a strong shock which cannot be handled only by the above magnetic lock mechanism or the like. When a weak shock is given, the above actuator hold mechanism holds the actuator because the inertial latch mechanism does not work, thereby increasing the reliability of the actuator lock mechanism.
As an example, the actuator lock mechanism using such inertial latch mechanism is shown in FIGS. 15 and 16. The actuator lock mechanism shown in FIGS. 15 and 16 uses a ramp of the load/unload mechanism as the actuator hold mechanism. In the inertial latch mechanism shown in FIG. 15, when a shock is given to cause an actuator 22 to rotate counterclockwise (to the disk 1 side), a latch lever 101 is rotated counterclockwise on a pivot by an inertial force, and a latch protrusion 102 abuts on the coil arm end 26c of the actuator 22 to latch the actuator 22. Further, the inertial latch mechanism shown in FIG. 16 uses two balls 202, and the two balls push a latch lever 201 by an inertial force and the latch lever 201 latches the actuator 22 centering a pivot.
An example of the actuator lock mechanism using the inertial latch mechanism is disclosed in Published Unexamined Patent Application No. 8-339645 by the applicant of the present invention. The actuator lock mechanism of Published Unexamined Patent Application No. 8-339645 includes an inertial latch mechanism as shown in FIG. 15, and includes as an actuator hold mechanism a magnetic or electromagnetic lock mechanism for latching the actuator by magnetism or electromagnetism.
A part provided on a pivot for free rotation, such as an actuator, is generally given a linear acceleration and an angular acceleration by an external shock. The force of a linear acceleration (translational force) works on the center of mass, and the force of angular acceleration (couple) works about the pivot. Assume a circle having a center which is the pivot, and which passes through the center of mass. It is assumed that the tangential component at the center of mass of the circle is an effective component, and the normal component at the center of mass is an ineffective component. Those which contribute to the rotation of the above part are the effective components of the angular acceleration and linear acceleration. The shock given to the actuator can be represented as shown in FIG. 11, in which the above angular acceleration A is the abscissa and the effective component Le of the above linear acceleration is the ordinate. A diagonally shaded region Ea in FIG. 11 is the region of a shock that can be given to the actuator.
When a large shock is given to rotate the actuator 22 shown in FIGS. 15 and 16 in the clockwise direction (opposite to the disk 1), the actuator bumps against a crash stop (elastic body) 5, and it may rebound to the disk 1 side. Accordingly, the shock regions for which the inertial latch mechanism must latch the actuator are diagonally shaded regions Eb1 and Eb2 shown in FIG. 12. However, in the actuator lock mechanism and the inertial latch mechanism which are shown in FIG. 15, when a shock is given to rotate the actuator 22 clockwise (to the crash stop 5 side), the inertial latch mechanism which reversely rotates does not work and cannot latch the actuator 22. That is, in the inertial latch mechanism as shown in FIG. 15, there are considerable dead zones, as shown by diagonally shaded regions Ee1 and Ee2 in FIG. 17. The dead zones mean the regions in which the inertial latch mechanism does not operate, in the diagonally shaded shock regions Eb1 and Eb2 (refer to FIG. 11) in which the inertial latch mechanism must operate. It can be said that an inertial latch mechanism having large dead zones has low reliability.
Further, in the inertial latch mechanism shown in FIG. 16, two balls are used to enable the inertial latch mechanism to operate regardless of the direction in which a shock is given, thereby to reduce such dead zones. However, as shown by a diagonally shaded region Ef in FIG. 18, a dead zone occurs when the roll acceleration A is considerably larger than the effective component Le of the linear acceleration, and to reduce the dead zone (region Ef), it is needed to make the mass of the balls larger or decrease the moment of inertia of the latch leaver. There is limitation on the decrease of the moment of inertia of the latch lever, and if the mass of the balls is made larger, it is difficult to mount the inertial latch mechanism on a thin-type disk drive device.
The present invention is to solve such background art problems, and its object is to provide an inertial latch mechanism for an actuator which is highly reliable and can be mounted even on a thin-type disk drive device.